Air blast circuit breaker



Nov. 22, 1955 H. FoRwALD AIR BLAST CIRCUIT BREAKER Filed Feb. 6. 1952l'un 4 Z l-IIH llll im Y* Am Am m Ik 20 m lll-"Ulli m. man l,

INVENTOR HHH/(0N For? WQLD ATTORNEY 2,724,751 Patented 22, 1955 AIRBLAST CIRCUIT BREAKER Haakon Ludvika, Sweden assigner -to Allmnn SvenskaElektriska Aktiebolaget, Vasteras, Sweden, a Swedish commotionApplication Febmary, 1952, Serial No. 270,169 Claims priority,application Sweden February 9, 19,51

4 Claims. l(Cl. 20G-#82) For the effective interruption of the currentin air blast circuit breakers it has proved to be of great importancethat the air intended to strike the arc at the separation of thecontacts is at rest before the streaming commences, so that there are nowhirls in it, when it reaches the arc. In the hitherto known air blastcircuit breakers the air is delivered to the breaking gaps throughrelatively long and narrow conducts or channels immediately before theinterruption shall take place. Under these circumstances it isimpossible to prevent the air from reaching the breaking gap in a ratheragitated state with plenty of whirls, and this is the case also if thebreaking gap is enclosed in an extinguishing chamber and is located in adistance from the point where the air enters the extinguishing chamber.The reason for this is that the volume of the extinguishing chambergenerally is so small that the air volume enclosed in it is insuicientfor the extinction, so that during the extinction period compressed airmust be delivered continuously to the extinguishing chamber. Thedisadvantageous inuence of such air whirls on the extinction of the arcis a result of the fact that the whirls in the aill cause a very unevenelectric strength of the air due to the formation of pockets in the airhaving a rather low pressure.

The present invention concerns an arrangement of air blast circuitbreakers by which the said disadvantage is avoided, and in accordancewith the invention, the breaking contacts are arranged in an aircontainer of metal carried by an insulating pillar and having a volumesucient to deliver with only a negligible pressure drop the whole airvolume necessary for an extinction, the contacts being arranged close toan outlet opening in the said container air blast.

The escape of the air from the container may be controlled either by thecontacts themselves forming an outlet valve, or this escape may becontrolled by a separate outlet valve arranged after the contactscounted in the direction of the air ow. The air container is furtherconnected by a relatively narrow pipeline with a source for compressedair, so that after the extinction the container again is lled with airwith the full pressure.

An especially advantageous construction can be attained if the aircontainer is arranged on an insulating pillar of a suitable design andone contact of the breaking gap is metallically connected with thecontainer, whereas the other contact is carried by an insulating bushingprojecting into the container. A circuit breaker having two breakinggaps in each air container is also possible, and in this case thecontainer has two outlet ducts which after the contacts may be joined toa -single channel which is provided with a single outlet valve. In thiscase the container contains two contacts carried each by its bushing,whereas the two other contacts of the contact pairs are metallicallyconnected with the container.

n the accompanying drawing a form of the invention is shown. On thedrawing 1 designates the compressed air container which by a conduct 2of insulating material is in communication with a source of compressedair tai-ner 1.

not shown on the drawing. 3 designates the stationary contact of thecircuit breaker which is attached `to the conductor 4 in the insulatingbushing 5. The movable contact 6 is of tubular form and is attached on a:piston 7, which moves in a cylinder 8 joined with the bottom 9 of thecompressed air container. The piston 7 is actuated upwards by a helicalspring l0. l11 is a sliding contact surrounding the tubular contact 6for carrying the current to the cylinder 8 and the bottom 9 of fthe oon-12 is ,the valve disc in an outlet valve which when in its #lower.position tightly rests against vthe ridge 13 on a cover 14. The valvedisc 12 is carried by a stem 15 which is joined with the operatingpiston L6 lfor the valve which piston is movable in the operatingcylinder 17 and actuated downwards by the helical spring 18. Thecylinder 17 is at its lower end closed by a bottom 19 attached to theinsulating pillar 20 carrying the circuit breaker. 21 is the operatingair pipeline which is made from some insulating material and is dividedinto two branches 22 and 23. When opening the circuit breaker,compressed air flows through the pipe 22 to the cylinder 17 below thepiston 16, and acts upwards on this piston against the counter-action ofthe spring 18, and when the piston 16 moves upwards, the valve disc 12is raised so that the air in the container 1 can escape into the openair through the openings 131. Simultaneously air ilows through the pipe23 against the operating member 24, which consists of a disc actuated bya diaphragm 25. When the operating member 24 moves upwards, a valve disc26 closes the pipeline 27 leading to the compressed air container andopens instead a communication 28 between the lower part of the cylinder8 and the open air. A part of the compressed air flowing upwards throughthe pipeline 23 will flow through the pipeline 29 into the upper part ofthe cylinder 17 for the purpose of moving the piston 16 to its lowerposition after the extinction has taken place and to thus close theoutlet valve 12, 13. The moment of closing is determined by the air owthrough the pipeline 29, which flow is regulated by means of therestriction screw 30. 31 is a non-return valve which allows a rapidemptying of the upper part of the cylinder 17 when the pipeline 21 isevacuated for the purpose of closing the circuit breaker.

The opening of the contact gap is performed by the compressed air in thecontainer 1 acting on the upper side of the piston 7 forcing itdownwards and compressing the spring 10. The air in the lower part ofthe cylinder 8 will then escape to the open air through the pipeline 28.

The motion downwards of the contact 6 is limited by striking the valvemember 12 and then the extinguishing air escaping through the lower endof the pipe will now escape through the side openings 32. By thisarrangement the breaking gap during the extinction period is maintainedcomparatively short but then is extended when the valve member 12 movesdownwards. When the piston 7 has reached its lowermost position, thechannel 28 becomes closed by the packing 33 on the lower side of thepiston 7 being forced against the two annular formed ridges 34 and 35.

The closing of the circuit breaker is performed by evacuating thepipeline 2l. When evacuatng this pipeline the valve disc 26 movesdownwards, so that the space in the cylinder 8 below the piston 7 bymeans of the pipelines 28 and 27 will be brought in communication withthe space in the container 1, and the pressure prevailing in thiscontainer will thus also be prevailing on the lower side of the piston7, so that it will be moved upwards by the spring 10 until the contacts3 and 6 are brought in contact with each other. Simultaneously the lowerpart of the cylinder 17 is emptied through the pipeline 22 and its upperpart through the back valve 31.

I claim as my invention:

1. An air blast circuit breaker comprising a metal compressed aircontainer having a capacity sutcient to contain a volume of air for atleast one current interruption, a pipeline delivering compressed air tosaid container, insulating means serving as the sole support for saidcontainer and insulating it from earth, an air outlet opening in saidcontainer, a pair of contacts in said container in close proximity tosaid outlet, an insulating bushing projecting into said container andcarrying one of the contacts of said pair, and valve means forcontrolling the ow of air from said container through said outletopening for opening and closing said contacts.

2. A circuit breaker according to claim 1, comprising means forconnecting one of said contacts electrically with said container.

3. A circuit breaker according to claim 2, comprising References Citedin the file of this patent UNITED STATES PATENTS 2,153,400 Trencham Apr.4, 1939 2,306,186 Rankin Dec. 22, 1942 2,447,656 Ludwig et al. Aug. 24,1948 2,491,112 Iansson Dec. 13, 1949 2,507,210 Ludwig et al May 9, 1950

